Characteristics of MaterialsAmerican Chemical SocietyWhat makes diapers absorbent? Is peanut butter stickier than syrup or jelly? Strong, stretchy, sticky, or sweet—everything around us has special properties which make them unique. See if you can identify and compare the characteristics of materials.

Principal Species and pHRobert M. HansonCalculates concentrations of principal species in solutions using JavaScript. You can specify whether "1st-year" methods or mass-charge balance methods are used in the calculations. Solutions can be chosen from the included set or you can design your own.

Acids / Bases |

Titration / Volumetric Analysis |

pH |

Solutions / Solvents

Computer Simulations of Salt SolubilityVictor M. S. Gil, João C. M. PaivaComputer Simulations of Salt Solubility provides an animated, visual interpretation of the different solubilities of related salts based on simple entropy changes associated with dissolution: configurational disorder and thermal disorder. This animation can also help improve students conceptual understanding of chemical equilibrium before any quantitative interpretation of equilibrium constants is attempted.

Computational Chemistry |

Solutions / Solvents |

Thermodynamics |

Equilibrium |

Precipitation / Solubility

Molecular Models of Compounds in Maple SyrupWilliam F. ColemanThis month's issue of J. Chem. Educ. includes articles by David Ball dealing with the chemical composition of honey (1) and maple syrup (2). The JCE Featured Molecules for this month are drawn from those papers. In prior months we have included sucrose, glucose, and fructose (3), and all of the naturally occurring amino acids (4) in the molecule collection. This month we add the molecules identified in Table 4 of ref 2 as probable contributors to the taste of maple syrup. This group of molecules could serve easily as a starting point for a variety of student activities in the area of taste. Students in non-majors courses could be asked to identify structural similarities and differences among the various molecules and could be introduced to functional groups. Students could look for other foods in which some of these molecules are found, and could begin to develop a list of molecules contributing to flavor. In the penultimate paragraph of the maple syrup paper there is a list of substances used as flavoring agents in artificial (maple) syrup. What molecules are in fenugreek and lovage that might be important in flavoring? What are the structures of the other molecules in that paragraph and what, if any, structural features do they have in common with the featured molecules? Students in organic or biochemistry courses could begin to explore the chemistry of taste in more detail. Good starting points for this work are The Chemistry of Taste: Mechanisms, Behaviors, and Mimics by Peter Given and Dulce Paredes (5) and the Chemical and Engineering News Web site (6), which includes a number of articles on this subject.

Descriptive Chemistry |

Solutions / Solvents |

Food Science |

Plant Chemistry

Chemical & Physical ChangeAmerican Chemical SocietyEverything you see and touch has the ability to change. Sometimes substances change to form new substances. This is called a chemical change. Other times substances change but keep the same identity. This is called a physical change. Try these activities to learn more about chemical and physical change.